The present invention relates to a high density recording technology, and more particularly to a magnetic recording medium having a layer structure for achieving a high signal output and a high recording resolution, and a manufacturing method of the same medium.
Recently, the magnetic recording medium has been intensively researched and developed as means of recording a huge quantity of information, and, in particular, the magnetic recording medium used in the hard disk device for computer is rapidly advanced in the areal recording density.
At the present, in this recording medium, the recording method of recording a signal by directing the magnetization vector in the in-plane direction of the recording film known as longitudinal magnetic recording is employed, but as a recording-method for realizing much higher recording density, perpendicular magnetic recording for recording a signal by directing the magnetization vector in the perpendicular direction of the recording film is attracting attention (see S. Iwasaki and Y. Nakamura, IEEE Trans. Magn., vol. MAG-13, pp. 1272-1277, 1997).
As the magnetic recording material, in either recording method, the Coxe2x80x94Cr alloy is mainly used in the recording layer. At this time, by a material, a crystal orientation, or a lattice constant of an underlayer, the crystal orientation of the Co-Cr alloy placed immediately on its underlayer can be controlled. It is therefore possible to control the direction of the easy axis of magnetization to determine the direction of magnetization vector. At the present it is intensively researched and developed about the longitudinal recording medium or perpendicular recording medium using the Coxe2x80x94Cr alloy thin film fabricated by such technique as the information recording layer.
By contrast to the information recording medium using the Coxe2x80x94Cr alloy thin film, Japanese Patent Application No. 10-162318 discloses layer structures of perpendicular magnetic recording media using a thin film of ordered alloy with L10 crystal structure excellent in thermal stability and large in magnetocrystalline anisotropy as shown in FIG. 10A, FIG. 10B, and its manufacturing method. According to this manufacturing method, the perpendicular magnetic recording medium is an information recording medium comprising an underlayer 40 mainly made of an element or a compound selected from Cr, Pt, Pd, Au, Fe, Ni, MgO or NiO, and an information recording layer 10 made of a thin film of ordered alloy with L10 crystal structure (hereinafter, the medium composed as shown in FIG. 10A is called single-layer perpendicular magnetic recording medium).
Further, for control of recording characteristic, the perpendicular magnetic recording medium is an information recording medium comprising a layer 30 made of Fe, FeSi alloy, permalloy or other soft magnetic material, and an information recording layer 10 made of a thin film of ordered alloy with L10 crystal (hereinafter, the medium composed as shown in FIG. 10B is called double-layer perpendicular magnetic recording medium).
This double-layer perpendicular magnetic recording medium is known to be increased in the signal output as compared the single-layer perpendicular magnetic recording medium, as reported by T. SUZUKI, N. HONDA, and K. OUCHI (1999 Digests of INTERMAG 99, AT-07).
In such double-layer perpendicular magnetic recording medium, however, as compared with the single-layer perpendicular magnetic recording medium, the signal output depends more on the recording density, and the recording density at which the signal output becomes half at low recording density (hereinafter called the resolution) is decreased, and this phenomenon is not preferred in high density recording using an actual signal output system.
So far, nothing has been proposed about the perpendicular magnetic recording medium using a thin film of ordered alloy with L10 crystal structure large in magnetocrystalline anisotropy satisfying both high signal output and high resolution.
It is hence an object of the invention to present an information recording medium having a high signal output and a high resolution, using a thin film of ordered alloy with L10 crystal structure large in magnetocrystalline anisotropy.
The invention is devised in the light of the present situation described above, and provides the following means for solving the problems and achieving the object.
A first aspect of the invention proposes a magnetic recording medium composed of a novel layer structure using a thin film of ordered alloy with L10 crystal structure achieving a high signal output and a high recording resolution as an information recording layer, and a manufacturing method of such medium, as set forth in the scope of claims.
As the magnetic recording medium, it is intended to present an information recording medium characterized by [1] having a layer structure sequentially forming a layer made of soft magnetic material, a layer made of nonmagnetic material, and information recording layer of ordered alloy with L10 crystal structure selected from group A (FePt ordered alloy, CoPt ordered alloy, FePd ordered alloy, and their alloy).
This information recording medium is the recording medium of [1], formed so that the Miller index (001) of the crystal lattice plane of the information recording layer of ordered alloy with L10 crystal structure selected from group A may be parallel to the plane of the recording layer.
It is also a feature of the recording medium of [1] that the nonmagnetic material is MgO. Or, in the recording medium of [1], the soft magnetic material is selected from group B (Fe, Fexe2x80x94Si alloy, Nixe2x80x94Fe alloy).
As a manufacturing method of this information recording medium, the invention presents a manufacturing method of information recording medium characterized by [5] sequentially manufacturing soft magnetic layer, nonmagnetic layer, and information recording layer of ordered alloy of L10 crystal structure selected from group A (FePt ordered alloy, CoPt ordered alloy, FePd ordered alloy, and their alloy).
This manufacturing method, in fabrication of the information recording layer of ordered alloy of L10 crystal structure, is the manufacturing method of [5], characterized by fabricating this information recording layer of ordered alloy of L10 crystal structure by the sputter deposition method using the sputtering target fabricated by melting method.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.